I needed to patch where the old gas door was, I made a piece of sheet metal to fit in the hole as tight as possible, then welded it in place.... making sure I did a little at a time to insure that the metal didn't warp.
Here is how it fits in the hole, now to mark the holes. I did that by spray painting the backside as you can see. Now I need to remove the gas tank again and do some more welding.....
Now I had to make the filler neck, it's got a few angles going on. I used a 2"- 90 degree exhaust pipe. It had to be cut and welded a few time, but should do the trick.